1. Field of the Invention
This invention relates generally to a torque transfer mechanism adapted to be incorporated in a multiple path drive system, for example, a four-wheel drive vehicle. More particularly, it relates to a system including an offset torque transfer case adapted to receive torque from a prime mover and to transmit torque to a plurality of drive axles.
2. Description of the Prior Art
In recent years there have been many improvements in automotive drive trains including improvements related to the transfer of torque from a prime mover to one or more drive axles. There has been a need to provide an improved torque transfer mechanism for establishing desirable low-speed high-torque and high-speed low-torque drive paths in four-wheel drive vehicles. At the same time there has been a need to provide such a mechanism which could be fabricated economically, and which would be quiet and efficient in operation.
Early torque transfer mechanisms generally provided only a rear wheel drive in the high-speed low-torque range, and a locked four-wheel drive in the low-speed high-torque range. Both ranges were generally gear drive trains which could be selectively engaged as desired. These gear drive trains were generally of heavy duty construction.
Later torque transfer mechanisms incorporated a center differential, which permitted four-wheel drive in both ranges, a chain drive train which could be engaged for direct drive and a gear drive train with which it could be engaged in series to provide reduction ratio torque. With the reduction, the chain carried the full torque load put through the mechanism. While normally, skid torque was the practical maximum limit for transfer through the chain drive train, under certain conditions an overload, possibly damaging to the chain, was possible.
Accordingly, it is an object of this invention to meet the continuing need and desire in the art for improvements in torque transmission by providing an improved torque transfer mechanism including parallel low-speed high-torque and high-speed low-torque drive paths, which has quiet operating characteristics, is efficient through a wide operating range, and is simple and economical to manufacture, operate and maintain. By providing parallel gear and chain drive trains, this invention allows flexible application of the improved torque transfer mechanism to vehicles with varied power requirements, and does so in a simple and economical manner.